I Killed a Mad Dog, and You Say I Slaughtered an Ancient Beast?

Thanks for the invite. I'm in the city, but the System insists this is a world of cultivation. One day, the System suddenly declares: [An ancient beast is rampaging ahead. Kill it and protect the civilians!] Su Yun: “Me?” When he kicks to death a rabid dog that was biting a child, the System says: [Congratulations on completing the quest. Constitution +1.] When he gets back to his apartment complex, the System announces: [The Sword Enthusiast challenges you. As the number one sword immortal of Shu Mountain, how can you back down? Defeat him!] Staring at the chuunibyou kid in front of him, clutching a glowing toy sword, Su Yun falls silent. He'd feel bad about actually fighting the kid, so he goes for a psychological attack instead, leaning close and whispering, “Actually, Ultraman doesn't exist.” The System: [Are you even human?]